This invention relates to .alpha.-amino acids having an .omega.-guanidino group wherein at least one of the guanidino nitrogens are substituted. More specifically, this invention covers arginine-type amino acids wherein one or both of the terminal guanidino nitrogens (H.sub.2 N--C.dbd.NH) is substituted.
In 1970, Kakimoto and Akazawa reported the isolation and identification of N.sup.G,N.sup.G' and N.sup.G,N'.sup.G -dimethyl-arginine from urine. This work was reported in J. Biol. Chem., 245, No. 21, 5751-5765 (1970). Subsequently, Patthy A., et al., reported the preparation and characterization of mono-, di-, and tri-methyl related arginines (Acta. Biochim. Biophys. Acad. Sci. Hung., 12 (3), 191-6 (1977).
It has now been discovered that substituting one or both of the guanidino nitrogens of amino acids such as arginine, homoarginine and related amino acids, provides an amino acyl residue which will increase the activity of a protein into which is incorporated and/or will increase the t 1/2 of that peptide.